The present invention relates to a high-tension power supply for an image recorder of the type adopting an electrophotographic procedure and, more particularly, to a high-tension power supply which allows its output current to be readily measured.
In a copier, facsimile apparatus, laser printer or similar electrophotographic image recorder, independent high-tension power supplies are installed for individually applying high voltages to various units which execute an electrophotographic procedure in cooperation. Typical of such high-tension power supplies are a power supply associated with a main charger for uniformly charging the surface of an image carrier in the form of a photoconductive element, a power supply associated with a transfer charger for transferring a toner image produced on the photoconductive element to a paper sheet by development, and a power supply associated with a discharger for dissipating a charge which remains on the photoconductive element after the image transfer. These power supplies are built in the image recorder at the production stage and then delivered with their outputs adjusted individually. Further, the outputs of the power supplies are checked at predetermined intervals while the image recorder is in use.
It has been customary to check the output of each high-tension power supply in terms of current by connecting an ammeter to the high voltage output side of the power supply. This kind of measurement has a drawback that the high voltage directly applied to the ammeter may cause an electric shock or damage the ammeter. Further, the high voltage brings about a substantial leak current which is apt to introduce errors in the measurement. Especially, concerning a high AC voltage, the loss due to distributed capacity is so great that the measurement is effected by the arrangement of leads and the location of an ammeter. The measurement should therefore be performed by determining minute conditions for measurement. Thus, the operation for checking the outputs of high-tension power supplies heretofore performed is extremely troublesome.